Clearly the Cuban missiles terrified Americans. However the US certainly did not regard either possession of nuclear weapons or basing them on territoreis of allies. As a matter of international law if there had been a bombing or invasion it would have arguably have been an illegal aggression. Interfering with shipping in international waters would have been an act of war and the US would clearly have been the power that started it. Stll had Kennedy (or maybe President Stevenson or Humphrey) protested but not threaened action would there have been an attempt to impeach?